This invention relates to a meat grinder, and more particularly to a meat grinder for performing a multiple stage grinding operation.
It is known to provide a meat grinding assembly which performs dual-phase grinding. One such assembly is shown in U.S. Pat. No. 4,003,521 to Hess. As shown in this patent, an adapter assembly is disclosed which incorporates a secondary orifice plate and a secondary knife assembly for providing a second phase of grinding at the discharge of a grinding machine. Another attachment mechanism for providing dual dualphase grinding is shown in U.S. Pat. No. 3,971,514 to Martinelli et al.
It is an object of the present invention to provide a retrofit assembly for a meat grinding machine which is readily adapted for use with a conventional feed screw provided on such a machine. It is a further object of the invention to provide such a retrofit assembly which incorporates a feature for biasing the primary and secondary knife assemblies against the primary and secondary orifice plates. Yet another object of the invention is to provide a retrofit assembly for a meat grinder which incorporates a unique drive system for driving the knife assemblies in response to rotation of the feed screw.
The retrofit assembly of the invention is adapted for use with a meat grinder having a rotatable feed screw to which one or more primary cutting elements are mounted at an end thereof adjacent a primary orifice plate. The end of the feed screw has a substantially central longitudinal bore extending throughout a portion of its length. In a single phase grinding operation, the longitudinal bore houses a compression spring which biases the primary cutting elements against the orifice plate. The biasing force provided by the spring is adjustable by means of a threaded bolt which extends through the primary cutting elements and the longitudinal bore in the feed screw and engages an end of the spring. In accordance with the invention, a double plate retrofit assembly for use in connection with such a meat grinder comprises a secondary orifice plate adapted for mounting downstream of the primary orifice plate and spaced therefrom. One or more secondary cutting elements are disposed adjacent the secondary orifice plate and downstream of the primary orifice plate. A mounting pin is provided for mounting the secondary cutting elements to the feed screw, and has a portion adapted for insertion into the longitudinal bore in the end of the feed screw. When so mounted, a portion of the mounting pin projects from the end of the feed screw. The projecting portion of the mounting pin is adapted to receive the primary and secondary cutting elements for mounting such cutting elements thereto. Drive means is interconnected with the projecting portion of the mounting pin for rotatably driving the primary and secondary cutting elements in response to rotation of the feed screw. In a preferred embodiment, an end of the mounting pin is seated at the end of the longitudinal bore in the feed screw. The drive means preferably comprises first engagement means disposed between the end of the feed screw and the primary cutting elements for rotatably driving the primary cutting elements in response to rotation of the feed screw. Second engagement means is disposed between the primary cutting elements and the mounting pin for rotatably driving the mounting pin in response to rotation of the primary cutting elements. Third engagement means is disposed between the mounting pin and the one or more secondary cutting elements for rotatably driving the secondary cutting elements in response to rotation of the mounting pin. The first engagement means preferably comprises one or more drive lugs provided on the end of the feed screw, and the second engagement means preferably comprises key means disposed between the primary cutting elements and the mounting pin for fixing the position of the cutting elements on the mounting pin means. A rotatable impeller is preferably disposed between the primary and secondary orifice plates and mounted to the mounting pin. The third engagement means preferably comprises impeller engagement means for rotatably driving the impeller in response to rotation of the mounting pin, and drive lugs formed on the impeller for rotatably driving the secondary cutting elements in response to rotation of the impeller. Spring means is preferably disposed between the end of the feed screw and the primary cutting elements for biasing the primary cutting elements against the primary orifice plate. Spring means is also provided between the impeller and the secondary cutting elements for biasing the secondary cutting elements against the secondary orifice plate.